What are the different type of solar water heater technologies available?

What are the different type of solar water heater technologies available?

Solar water heaters differ in terms of the collector technologies used and the design & construction of the system to suit specific applications.

Solar Water Heaters – Classified Based on Type of Collectors:

Basic solar water heaters are of two types depending upon the collector technology used: Flat Plate Collector (FPC) type and Evacuated Tube Collector (ETC) type.

Flat Plate Collector based solar water heater

Flat Plate Collector based solar water heater                             

The Flat Plate Collector consists of an insulated metallic box covered on the top with toughened glass. The metallic box contains an absorber sheet (normally made of copper) that is coated with a selective coating toincrease the absorption of solar energy. Vertical tubes made of copper, known as riser tubes are attached to the absorber and carry the water to be heated. The riser tubes are connected to two horizontal tubes called headers, one placed at the bottom and the other at the top. The bottom header is used for flow of water into the collector whereas the top header is used to take out the heated water.

Cold water enters the storage tank, fills it up and then flows to the collector through the bottom header and into the riser tubes, until all the absorber tubes and the header at the top are full. When the sun shines, the heat energy is absorbed by the absorber and transferred to the water in the riser tubes. The heated water being lighter than the cold water rises and via the top header pipe flows into the storage tank. More cold water flows into the collector, gets heated and rises to the top, and so on. This process known as the “Thermosyphon process” continues until the temperature of the water in the storage tank and the collector equalizes. Hot water is stored in the insulated storage tank and is available for use as and when required.

To view the FPC solar water heater models selling on Glowship, click here

 

Evacuated Tube Collector based solar water heater

                 Evacuated Tube Collector based solar water heater 

The Evacuated Tube Collector consists of two co-axial glass tubes fused at both ends with air between the tubes evacuated to create vacuum that works as insulation. The outer surface of the inner tube forms the collector area and it is selectively coated to increase the absorption of solar energy.

Cold water enters the storage tank, fills it up and then flows into the individual tubes until all the tubes are full. When the sun shines, the heat energy is absorbed and transferred to the water in the inner tube. The heated water being lighter than the cold water rises and flows into the storage tank. More cold water flows into the collector, gets heated and rises to the top, and so on. This process known as the “Thermosyphon process” continues until the temperature of the water in the storage tank and the tube equalizes. Hot water is stored in the insulated storage tank and is available for use as and when required.

To view the ETC solar water heater models selling on Glowship, click here

In addition, in both these types of technologies variantsare available tosuit specific applications:

Solar Water Heaters – Classified Based on Type of Application:

Normal Applications:

These systems are the basic models (available in both ETC & FPC type systems) and are used when the system is operating under atmospheric pressure (i.e. there are no pressure pumps being used to pump water out of the storage water tank).

Click here to view solar water heaters suitable for soft water (water hardness < 300ppm) and normal applications.

Click here to view solar water heaters suitable for hard water (water hardness 300ppm – 600ppm) and normal applications.

Click here to view solar water heaters suitable for extreme hard water (water hardness > 600ppm) and normal applications.

Pressurized Applications:

These systems can withstand the higher operating pressure that exists due to the use of a pressure pump in the water circulation system. Pressurized systems are suitable when:

  • The height of the overhead tank carrying cold water is less than 7 ft above the terrace
  • High pressure hot water flow is required for various uses like jet showers, shower panels etc
  • The number of hot water points are more than normal 

The pressure rating of these types of systems varies from 3 bar upto 8 bar.

Click here to view solar water heaters suitable for soft water (water hardness < 300ppm) and normal applications.

Click here to view solar water heaters suitable for hard water (water hardness 300ppm – 600ppm) and normal applications.

Click here to view solar water heaters suitable for extreme hard water (water hardness > 600ppm) and normal applications.

Hard water suitable systems:

This type of system is used in cases where there is hard water or where the ambient temperatures are low enough to cause water freezing. In such cases, distilled water is used as the heat transfer medium and is circulated in a closed loop system through the solar fins or tubes and goes back into the top of the outer tank where it transfers its heat to the cold water in the inner tank.

The water hardness tolerance level for the different type of systems varies from 600ppm to 1200ppm.

Click here to view solar water heaters with heat exchanger type tanks

Optional features:

The following optional features are available with all kinds of water heaters:

Electrical back-up heater:

Most solar water heaters come with the provision of an electrical back-up heater that can be used to heat water on cloudy days when enough sunshine is not available to heat the water to the desired temperature.

Sacrificial anode:

The sacrificial anode rod made of Aluminium/Magnesium is screwed to the storage tank and protects the tank against galvanic corrosion. For long life of the storage water tank it is advisable to replace the anode rod from time to time. Magnesium anodes in general protect the tank for a longer duration compared to Aluminium anodes.
Click here to choose from different brands of solar water heaters based on the type of collector / application / water hardness & other useful parameters

Purchase a Solar Water Heater